A web console for Rack apps.

gem install rack_web_console -v 0.1.4


Rack Web Console Build Status

Rack Web Console is a simple Rack app class that allows one to run arbitrary Ruby code on a given binding, which may be useful in development mode to test some code in a given context. This is similar to the rails-web-console (it was indeed extracted from it with a few enhancements) but works for any Rack based application, including Rails.


Add this line to your application's Gemfile:

gem 'rack_web_console'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack_web_console


The hello world is not much useful, but here you are:

# config.ru
require 'rack_web_console'
run RackConsole.new binding

Usually, you'd be more interested in learning about the binding which is usually a controller or something like that. For example, if you want to test code from inside a Roda's route block:

# config.ru
require 'roda'
require 'rack_web_console'

class App < Roda
  route do |r|
    r.on('console'){ halt RackConsole.new(binding) } if ENV['RACK_ENV'] == 'development'
    'default response'

run App

The local variable r would be available in the console for example in this case. Some frameworks may not have a method like Roda's halt, so in a Rails application for example, you may have to do this:

# app/controllers/console_controller.rb:
require 'rack_web_console'
class ConsoleController < ApplicationController
  skip_before_action :verify_authenticity_token

  def index
    status, headers, body = RackConsole.new(binding).call(env)
    response.headers.merge headers
    render inline: body.join("\n"), status: status

# routes.rb:
Rails.application.routes.draw do
  # ...
  match 'console' => 'console#index', via: [:get, :post] if Rails.env.development?

The rails-web-console gem is probably a better gem to use with Rails but this example should demonstrate how it could be used with basically any framework. If you're not really interested on some specific binding, you can simply mount it directly in config.ru:

# config.ru
require_relative 'config/environment'

require 'rack_web_console'
map('/console'){ run RackConsole.new }

run Rails.application

By default, only the output of the request thread is sent to the POST request response. If you want to spawn new threads from the script and see the output of all threads, set the :rack_console_capture_all thread local to true:

Thread.current[:rack_console_capture_all] = true
Thread.start{ puts 'now it should be displayed in the browser' }.join

Shortcuts from inside the textarea

  • Ctrl+Enter: Run code
  • Esc, Esc: Clear output


After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.


Bug reports and pull requests are welcome on GitHub.


The gem is available as open source under the terms of the MIT License.